A test for comparing the means of two samples, or the mean of one sample (or even parameter estimates) with a specified value; also known as the "Student t-test" after the pseudonym of its inventor.

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24 views

Running many $t$-tests to find the most significant way to divide a dataset

I apologize for my stats illiteracy in advance–I'm not a stats guru by any stretch, but am trying to learn. To start, I'll just introduce what my data set looks like, then what I'd like to ...
2
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1answer
19 views

Compare group mean to larger group of which it is part

I have thousands of evaluation scores, over several sites, which vary in number of evaluations for each. I am tasked with comparing the evaluation means for each site to the all-site mean. The ...
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2answers
36 views

Beyond a Welch's t-test

I have two groups of species: the groups have different numbers of species. For each species, a different number of individuals have been screened for a gene. I want to describe the difference for ...
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1answer
31 views

Wald test on marginal effect

Say I have the following regression equation: $$Wage_i = YearsOfEduc_i + Age_i + NumOfSiblings_i + u_i$$ How would I go about peforming a wald test of the hypothesis that for an individual with ...
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0answers
9 views

Significance test for longer pronounciation

I have a set of words spoken by a group of native speakers and a group of non-native speakers. In each record I determined the length of the burst (a phonetic term). I believe non-native speakers tend ...
2
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1answer
57 views

Confidence Intervals Around a Mean: biased (non-centered) confidence interval? (an exercise using R)

I've been playing around with the module "Confidence Intervals Around a Mean" (meanCI) from statsTeachR (www.statsteachr.org), authored by Eric A Cohen (unfortunately, author's contact information was ...
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1answer
100 views

Is Student's t test a Wald test?

Is Student's t test a Wald test? I've read the description of Wald tests from Wasserman's All of Statistics. It seems to me that the Wald test includes t-tests. Is that correct? If not, what makes a ...
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2answers
31 views

If one group has 23 participants and the second group has 117 participants in it, can we rely on the result of t-test? [duplicate]

I was evaluating a research paper in which the authors have 23 male participants and 117 female participants. They have applied t-test to calculate Gender differences and have even concluded on ...
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1answer
40 views

What statistic to use

My 8 year old daughter is conducting an experiment to assess memory. She has 3 groups. Condition 1, Condition 2 and ...
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1answer
11 views

What should I use to run a pre and post after intervention with a control group 15 participants?

I want to know the effect of reflective video analysis on teacher intentions to stay or leave the teaching position, teacher efficacy, and teacher job satisfaction in rural middle schools. I will ...
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1answer
31 views

When testing for a difference between effect sizes, is test power affected by their respective magnitude?

When comparing two effect sizes with a statistical test, does it matter for the test's power whether these effect sizes themselves are large or small? Imagine you are planning an experiment in which ...
3
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1answer
19 views

Pre-post analysis with multiple post measures

I am having trouble deciding what type of analysis to use for the following data: I have two groups (one control, one treatment) and took a pre-measure of my dependent variable, and then 3 ...
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20 views

Significance of linear combination of two insignificant regression parameters

I'm running a model with an interaction term, of the general form: $Y=b_1X_1+b_2X_2+b_3X_1X_2$, whereby $X_2$ is a dummy variable and $X_1$ is continuous. Neither $X_1$ nor $X_2$ turn out as ...
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20 views

What statistical test to use for A/B testing

I'm trying to understand how A/B testing works for a simple 2x2 contingency table. I have found two different types of solutions: 1) Calculate an aggregate probability of conversion assuming that ...
2
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1answer
46 views

One sample $t$-test with range values

I need to compare an average value for an experimental group ($n=5$) with a reference value given by legislation. But this reference value in given as [min - max] range. Do I have to compare my ...
0
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1answer
34 views

Reproducing simple t-test result with ANOVA

We know that a t-test is just a special case of ANOVA, so I tried to reproduce the result of the following t-test with aov() or ...
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1answer
26 views

Random variable variance

I have the model $y_i=\beta_1+\beta_2 X_i+ u_i$ where $u_i\sim\text{iid } N(0,\sigma^2)$. I estimate $\beta_1$ and $\beta_2$ by drawing a straight line between the first $(x_1,y_1)$ and last dot ...
2
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1answer
30 views

wilcox.test usage in R

I would like to know if there is a difference in the values taken from measurements of a given characteristic sampled at primary forest (Point=1) and secondary ...
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1answer
33 views

Is Student's $t$-test the right choice?

I have 2 patient populations taken from the same time period that underwent 2 different surgical laparoscopic procedures. I want to compare the rate of conversion to an open surgical procedure. In my ...
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0answers
12 views

Mixed model approach to one sample tests

Is it possible to use the mixed-models approach to test if the mean of a sample is significantly different from zero? I know that mixed models, with crossed random effect for target, and subject, are ...
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2answers
125 views

Mann Whitney test with unequal variances [duplicate]

I am confused on what I have read about the Mann whitney test. We are testing whether our actual data is the same as our projected data. We had been using the t-test until we realized the data might ...
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1answer
35 views

Which statistical test is appropriate for determining whether there is a significant difference in the exam scores of 2 groups(abnormal distrib)?

Male exam scores 58 54 61 64 60 60 45 44 53 54 32 56 43 69 69 72 66 45 63 49 48 53 Female exam scores 71 55 42 49 57 51 51 60 60 60 51 43 41 24 43 48 57 79 73 53 53 64 54 59 73 47
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1answer
68 views

Non-parametric version of paired t-test (Mann–Whitney U test)

I have data from 100 individuals doing a 2AFC under a control and a manipulated setting. I want to compare the means. I initially used a paired t-test. My supervisor noticed the distributions were not ...
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80 views
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43 views

If my normality test is non-significant, am I safe to use the t-test?

I took a 30 unit sample from a population. The sample distribution resulted to be normal. Can I state that the population distribution is normal too? If so, with what level of confidence?
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1answer
28 views

Paired t-test with subsamples in R?

I've been trying to find a similar "problem", but I didn't, so I'm going to try to explain what am I looking for. I have for different sites A,B,C and D. In each site I have a forest and a fallow=> ...
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1answer
33 views

t-test on seasonal effects on water quality

I am confused in the use of t-test. I monitored physical parameters of a river water two time (from the same site)- during winter and summer. Now I want to see the seasonal difference on physical ...
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0answers
22 views

Non parametric anova or two non parametric ttest?

I have a statistical question about a project I recently got. We performed a flow cytometry assay on 3 different groups: controls (n=5), patients before treatment (n=5) and paired patients after ...
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10 views

Determining dependancy of observations

I have 12 people, 6 in treatment group and 6 in control group. They gave ratings (1 to 7) to 8 different activities they were performing as a part of the experiment. I looked at another thread here ...
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0answers
42 views

Should I use independent samples t-test?

I need to analyse if there's a difference between poor and rich European countries (using a GDP per capita index variable) and look if it has an effect on the variable environment. The GDP per capita ...
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0answers
17 views

Difference test for beta–binomial variables

Let $X \sim \textrm{Beta–Binomial}(\alpha_1, \beta_1, n)$ and $Y \sim \textrm{Beta–Binomial}(\alpha_2, \beta_2, n)$ and write $\mu_1 = \frac{\alpha_1}{\alpha_1 + \beta_1}$, $\phi_1 = \alpha_1 ...
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27 views

Should I use both paired t-test and intraclass correlation coefficient to examine the interrater reliability of an instrument?

As title, I am assessing the interrater reliability of a questionnaire (actually a Barthel Index (BI)) performed by four assessors (A,B,C,D) on about 25 test subjects. I plan to examine the IRR from ...
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0answers
11 views

How to analyze this design? Multiple batches of Single group pre-test post-test designs

first of all - thanks for reading this. I have a want to analyze the effect of an intervention, but due to practical circumstances I cannot randomly assign people to it and the interventions differ ...
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3answers
61 views

Test model coefficient (regression slope) against some value

In R, when I have a (generalized) linear model (lm, glm, gls, ...
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2answers
253 views

What is the p-value for paired t-test if the two set of data are identical

As title, I have two set of data that are identical and performed paired t-test using R, the p-value for the difference estimated (which is essentially 0) is NaN. I wonder if there can be a ...
3
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3answers
151 views

Should I use t-test on highly skewed and discrete data?

I have samples from a highly skewed dataset about users' participation (e.g.: number of posts), that have different sizes (but not less than 200) and I want to compare their mean. For that, I'm using ...
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0answers
15 views

How to apply Shapiro test in R? [duplicate]

I'm pretty new to statistics and I need your help. I just installed the R software and I have no idea how to work with it. I have a small sample looking as follows: ...
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4answers
272 views

How exactly does null hypothesis testing work

I'm trying to gain a better understanding of how null hypothesis testing works. I have 3 questions related to the code below: Am I right in saying the probability of each t value in ...
6
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1answer
697 views

Should I use t-test on highly skewed data ? Scientific proof, please?

I have samples from a highly skewed (looking like an exponential distribution) dataset about users' participation (e.g.: number of posts), that have different sizes (but not less than 200) and I want ...
2
votes
2answers
29 views

Multiple comparisons with t-test: one group with different variance

If I have 3 groups that I want to compare with a t-test (correcting for multiple comparisons afterwards) but one of the groups has different variance than the other two, should I use a Welch ...
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0answers
9 views

MV GARCH DCC - t-test with high t-statistics

I use multivariate GARCH DCC to compute volatilities of 3 (stationary, supposedly) time series. Then I test the differences between these three volatility series with t-test and get very high ...
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10 views

Is it advisable to use t test for comparing two modules in SAP?

I have two independent samples from the maintenance and materials departments regarding the effectiveness of SAP modules. I have a likert scale data on a scale of five. Shall I use independent sample ...
2
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2answers
141 views

Two-Sample t-Test for Equal Means with unequal variances for large samples

How can I perform a two sample test of means with unequal variances for a very large sample in R? In case of large samples the statistic will asymptotically follow a normal distribution. Which R ...
2
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3answers
78 views

How do I compare sample means in this experimental-control group study?

I am hoping to compare the sample mean of an experimental group to the sample mean of three control groups. Here is some context for the study: The experimental group consists of ~60 persons with a ...
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1answer
102 views

$t$ test vs $\chi^{2}$ once sample is split into two groups?

I would appreciate some guidance regarding the use of a t test vs $\chi^{2}$. I am looking at some small set of demographic data (n only 13). I have divided up the sample into two sets, those with ...
1
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1answer
66 views

Paired $t$ test - Different Sample size

In testing the difference between a 'pre' survey group and 'post' survey group, I have the same sample population surveyed, yet different sample sizes (fewer respondents within the 'post' group). Am I ...
0
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0answers
24 views

Test for two confidence intervals

I would like to know if there is a test for the difference of to means m1 and m2 (continuous variables) if I have only information for mean, 2.5%- and 97.5%-quantiles. For example: $m1 \ \ \ = ...
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0answers
16 views

How to do mean comparison with trending data?

A client with a website has recently released a tablet app. The theory is that after installing the app a customer is less likely to log on to the website as they will use the app instead. For each ...
0
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1answer
30 views

Understanding Regression vs. Means/Median Results

I am having a little difficulty understanding my results - could someone help me understand how to interpret, and if my process is sensible? Here is an example of what I am doing I am trying to ...
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1answer
21 views

Is my (SPSS) independent t test correct, and how should I intrepret it?

I have a sample size of 158 students belonging to IT(N=77) and non-IT disciplines(N=81). I have carried out the independent sample t-test but I am not sure whether it's correct or not. Moreover, ...